A242765 a(1) = 2; for n>1, a(n) = product of digits of (a(n-1)^2).

2, 4, 6, 18, 24, 210, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

1,1

Links

Table of n, a(n) for n=1..72.

Example

6 is in the sequence because 4^2=16 and 6*1=6.
18 is in the sequence because 6^2=36 and 3*6=18.
Other similar sequences, starting from 3, 5 and 7, respectively:
. 3, 9, 8, 24, 210, 0 (0 continued);
. 5, 10, 0;
. 7, 36, 108, 144, 0.

Mathematica

a[1] = 2; a[n_] := a[n] = Times @@ IntegerDigits[a[n - 1]^2]; Array[a, 100] (* Jean-François Alcover, May 29 2014 *)
NestList[Times@@IntegerDigits[#^2]&, 2, 80] (* Harvey P. Dale, Aug 23 2017 *)

Crossrefs

Cf. A163522.

Sequence in context: A064402 A268577 A075229 * A073664 A088174 A052930

Adjacent sequences: A242762 A242763 A242764 * A242766 A242767 A242768

Keyword

nonn,base,easy

Author

Vincenzo Librandi, May 29 2014

Status

approved